Process for the recovery of silica, alumina, and potash from feldspar.



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SAMUEL PEACOCK, OF BALTIMORE, MARYLAND, ASSIGNOR TO AMERICAN ACID COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF MAINE.

PROCESS FOR THE RECOVERY OF SILICA, ALUMINA, AND POTASH FROM FELDSPAR.

rea ies.

No Drawing.

Specification of Letters Batent.

Application filed April 8, 1911.

Patented JuneilS, 1912. Serial No. 619,828.

To all whom it may concern:

Be it known that I, SAMUEL PEAoooK, a citizen of the United States, residing at Baltimore, in the State of Maryland, have invented certain new and useful Improvements in Processes for the Recovery of Silica, Alumina, and Potash from Feldspar; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a process for the recovery of silica alumina and potash from feldspar or from their otherwise naturally occurring combinations or associations and in which they are insoluble in water or in acids, or in other inexpensive solvents, and it has for its object to produce a process which will recover these compounds in a manner simpler, more expeditious and less expensive than heretofore proposed.

To these ends the invention consists in the novel steps constituting my process more fully hereinafter disclosed and particularly pointed out in the claims.

It is well known that the silica, alumina, potash and soda in feldspar is in such a condition that they have practically no commercial value beyond the use of this mineral in porcelain manufacture. The silica however, if rendered soluble and separated from the other oxids would be valuable as a cementitious product, or for glass making, as well as in other relations. The alumina if separated would be valuable for making alum cakes, metallic aluminum, as well as for the manufacture of certain abrasives, &c., while the potash if separated from the silica and alumina in such a form as to be soluble in water would be valuable as a plant food, in glass making, and in various chemical preparations requirng potash as an essential base or constituent. In other words, a ton of feldspar is worth industrially at best about $3.00, while its individual constituents separated as above would probably be worth industrially $25.00.

\V hat is said above in connection with feldspar is also true in a somewhat lesser degree in regard to the various micas and silicious and aluminous minerals such as glauconite, rhyolite, leucite, \Vyomingite, orendite, and generally in regard to all those naturally occurring minerals containing relatively large amounts of silica alumina, potash, or any two or these oxids. My process accordingly, is applicable to each and all of these mlnerals. I

In carrying out my invention I will illustrate the employment of feldspar as an example for the base material, and when this material is used I reduce the same to a coarsepowder and if crystalline I calcine it in any suitable furnace in order to convert it into the amorphous form. I then add to the calcined mineral a concentrated solution of potash or soda carbonate in such quantity that the alkali of the solution together with the alkali occurring naturally in the mineral itself is present in chemical equivalents equal to the silica for each hundred pounds of silica there must be present 160 pounds of alkali, or in chemical proportions, of not more than two equivalents of potash to one equivalent of silica. The mixture of calcined mineral is ground to a fineness of not less than say 100 mesh as is usually done in the manufacture of Portland cement, and the resulting pulp is introduced into a digester or'autoclave and treated with'superheated steam at a pressure of substantially 5 atmospheres, and until all the silica present is converted into potassium or sodium silicate or both. The time of this digestion will vary, and depend upon the nature of the raw materialunder treatment, but it must be continued until all the silica present is converted into alkali silicates that are soluble in water.

At the end of the digestion process the contents of the digester is discharged into a suitable receiver and cooled, an air blast being preferably used for accomplishing the cooling. lVhen cooled the solution of alkaline silicate is removed from the insoluble alumina by decantat-ion or by a suitable filtration method. All of the alumina now remains as an insoluble hydrate, which contains a small percentage of the alkali used. The alumina pulp is then washed with water in an autoclave or other apparatus, and at substantially -5 atmospheres pressure or above, and treated while under this ressure with sufiicient carbon dioxid C 2 to convert all the alkali present into carbonates. The contents of the digester may be discharged directly into a filter press or other apparatus, and thoroughly washed with hot water, the washings beingcollectpresent. That is to say,

' manner or otherwise prepared for industrial uses. The soluble alkalinesilicates' re sulting from this process are also treated 'with carbon dioXid CO for a time suflicient to convert all the alkali present into carbonates. The carbonated solution after cooling is treated for the separation of soluble alkaline carbonates and insoluble gel'atinous silica by any suitable centrifugal or other apparatus, or they may be separated in a powerful filter press. The solution of alkaline carbonates obtained, may be concentrated for crystallization of the alkali in the form of carbonates in the usual manner, and the resulting mother liquors may be returned to the process. I

It will thus be seen that by the process above disclosed, the alumina is isolated as such in a high state of purity, the silica is removed as an insoluble precipitate in a high'state of purity, and in a highly active form for further use as an acid, while the potash or soda is collected in solution as a carbonate from which it may be largely removed in a high state of purity by concentration and crystallization. Further, it will be seen that all the incompletely isolated elements will collect in the mother liquors of the potash of soda, and as these are all returned to the process, there are no losses of mineral values. Further, if iron is present, it will separate with the alumina from which it may be isolated by any Well known process.

What I claim is 1. The process of obtaining silica, alumina and potash from feldspar, which confrom the insoluble alumina present; treating said alumina with carbon dioxid to convert any alkali it may contain into a parbonate, and dehydrating the substantially pure alumina thus obtained; treating said soluble silicates with carbon dioxid to converttheir contained alkalies into carbonates; and finally separating said carbonates from the silica present, substantially as described.

2. The steps in the art of obtaining silica, alumina and potash from feldspar, which consists in convertin the feldspar into the amorphous form; adding su'fiicient alkali to cause the mixture to contain not more than two and not less than one equivalent of alkali to each equivalent of silica; treating the material with superheated steam to form therein soluble alkali silicates; separating from said silicates the alumina contained in the mixture; separating out any alkali that may be contained in the alumina; and suitably decomposingsaid silicates forming al-. kali carbonates and .recovering the contained alkali, substantially as described.

In testimony whereof, I aflix my signature, in presence of two witnesses.

SAMUEL 'P'EAoooK.

Witnesses T. A. WrrmiRsrooN, V R. M. PARKER. 

